Operating Systems - Page Replacement - FIFO, LRU, Optimal Algorithm
A system uses FIFO page replacement with 2 frames and the reference string: 1, 2, 3, 2, 1, 4. How many page faults occur?
A system uses FIFO page replacement with 2 frames and the reference string: 1, 2, 3, 2, 1, 4. How many page faults occur?
medium🧠🧾 Concept Trace Q4 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace FIFO faults
Frames empty initially. Insert 1 (fault 1), 2 (fault 2). Next 3 replaces 1 (fault 3). Next 2 is hit. Next 1 replaces 2 (fault 4). Next 4 replaces 3 (fault 5). Total faults = 5.Final Answer:
Option D -> Option DQuick Check:
FIFO evicts oldest, counting faults carefully [OK]
Quick Trick: FIFO evicts oldest, count faults on misses [OK]
Common Mistakes:
MISTAKES- Counting hits as faults
- Misordering eviction sequence
- Off-by-one counting errors
Trap Explanation:
PITFALL- Candidates often misapply FIFO eviction order or confuse hits with faults.
Interviewer Note:
CONTEXT- Verbal tracing of FIFO eviction and fault counting.
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